Newcastle, Margaret, Duchess of (1624?-1674). -- Dau. of Sir Thomas Lucas, and a maid of honour to Queen Henrietta. Maria, m. in 1645 the 1st Duke of Newcastle (then Marquis), whom she regarded in adversity and prosperity with a singular and almost fantastic devotion, which was fully reciprocated. The noble pair collaborated (the Duchess contributing by far the larger share) in their literary ventures, which filled 12 vols., and consisted chiefly of dramas (now almost unreadable), and philosophical exercitations which, amid prevailing rubbish, contain some weighty sayings. One of her poems, The Pastimes and Recreations of the Queen of Fairies in Fairyland has some good lines. Her Life of her husband, in which she rates him above Julius Cæsar, was said by Lamb to be "a jewel for which no casket was good enough."